chore: add favicon in .ico format

[mxschmitt]

Motivation: .svg favicons don't work in Safari, looks like they have no plans to support SVGs there.

For reference on how to obtain this file:

# Generate all the required PNG sizes with transparency using rsvg-convert
rsvg-convert -h 256 static/img/playwright-logo.svg > icon-256.png
rsvg-convert -h 128 static/img/playwright-logo.svg > icon-128.png
rsvg-convert -h 64 static/img/playwright-logo.svg > icon-64.png
rsvg-convert -h 48 static/img/playwright-logo.svg > icon-48.png
rsvg-convert -h 32 static/img/playwright-logo.svg > icon-32.png
rsvg-convert -h 16 static/img/playwright-logo.svg > icon-16.png

# Combine all sizes into a single ICO file using ImageMagick
magick convert icon-256.png icon-128.png icon-64.png icon-48.png icon-32.png icon-16.png static/img/playwright-logo.ico

# Clean up the temporary PNG files
rm icon-256.png icon-128.png icon-64.png icon-48.png icon-32.png icon-16.png

[github-actions]

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